How are phone numbers indexed and searched within WhatsApp's systems?

[muskanhossain]

WhatsApp likely employs a multi-layered approach to indexing and searching phone numbers within its systems to facilitate various functionalities while aiming for efficiency and security. Here's a breakdown of the probable methods:

1. Direct Indexing for Account Identification:

The primary index for a WhatsApp account is undoubtedly the user's phone number. When a user logs in or when the system needs to retrieve account-specific information, the phone number serves as the unique key to access their profile data, settings, contacts, and associated information. This likely involves highly optimized, direct indexing within WhatsApp's primary user database.
2. Hashed Indexing for Contact Discovery:

For the contact discovery feature, where WhatsApp identifies which of a user's address book contacts are also on WhatsApp, a different approach is used for privacy reasons. When a user syncs their contacts, the phone numbers are cryptographically hashed (transformed into a fixed-size string of characters that cannot be easily reversed to the original number).
WhatsApp likely maintains an index of these hashed phone numbers. When a new user joins, their phone number is also hashed, and this hash is compared against the existing index to identify potential connections. This allows for efficient matching without WhatsApp directly storing or comparing the raw phone numbers of non-users.
3. Inverted Indexing for Search Functionality:

While WhatsApp's search functionality primarily focuses on message vietnam whatsapp number data content and contact names, phone numbers might also be part of an inverted index associated with user profiles.
An inverted index maps keywords (in this case, digits of a phone number or full phone numbers) to the documents (user profiles) that contain them. This allows for faster searching when a user types in a phone number in the contacts or new chat search bar.
4. Distributed Indexing for Scalability:

Given WhatsApp's massive user base, the indexing and search infrastructure would need to be highly distributed across multiple servers and data centers to handle the load and ensure low latency. Technologies like sharding (splitting the database into smaller, faster, more easily managed parts) are likely employed to distribute the index and search operations.
5. Caching Mechanisms:

To further improve search performance for frequently accessed contacts or recently searched numbers, WhatsApp likely uses various caching mechanisms. This could involve storing frequently accessed portions of the index in memory for faster retrieval.
6. Security Considerations in Indexing:

While efficiency is crucial, security is paramount. WhatsApp would implement measures to protect the phone number indexes from unauthorized access and manipulation. This could involve access controls, encryption at rest, and regular security audits.
In summary, WhatsApp likely uses a combination of direct indexing for account identification, hashed indexing for privacy-preserving contact discovery, and potentially inverted indexing for search functionalities. These indexes are likely distributed and supported by caching mechanisms to ensure scalability and performance, with robust security measures in place to protect the sensitive phone number data. The specific database systems (like Mnesia, SQLite, Cassandra, etc.) they use would have built-in indexing capabilities that WhatsApp engineers would leverage and optimize for their specific needs.